1. Field of the Invention
The present invention relates to a silicon optoelectronic device and an optical signal input and/or output apparatus using the same. More particularly, the present invention relates to a silicon optoelectronic device capable of both emitting and receiving light and an optical signal input and/or output apparatus, i.e., an optical transceiver, using the same.
2. Description of the Related Art
Silicon semiconductor substrates can be used to highly integrate devices, such as logic devices, operation devices, drive devices, therein, with excellent reliability. Since silicon is inexpensive, these highly integrated circuits can be formed at a much lower cost than using a compound semiconductor. For these reasons, silicon (Si) is currently used as a base material for most integrated circuits.
Due to this prevalent usage and numerous advantages, attempts have been made to create optoelectronic devices in silicon. However, silicon has an indirect transition band gap that makes photoelectric conversion difficult. Thus, optoelectronic devices, such as light-emitting devices, e.g. a light-emitting diode (LED), are usually fabricated using a compound semiconductor material that has a direct transition band gap, allowing easy realization of photoelectric conversion.
A light-emitting device emits light only when a current above a critical current is applied thereto. Typically, supply of current at an appropriate level to the light-emitting device requires an amplifying circuit and/or a switching circuit. The amplifying circuit amplifies a small intensity of current to a current level appropriate to oscillate the light-emitting device and the switching circuit controls on/off operation for the light-emitting device.
Due to the resultant semiconductor heterojunction, it is impractical to integrally fabricate a device made of a compound semiconductor and a device made of silicon. Therefore, the amplifying circuit and/or a switching circuit must be fabricated separately from and installed external to the light-emitting device. However, parasitic effects of reactance and capacitance in the external power lines make realization of high-speed switching difficult.
Further, when using an array of light-emitting devices made of compound semiconductor materials as a display device, the external switching circuits control light emission on a pixel-by-pixel basis. However, this external provision makes it difficult to control the turn-on and turn-off time of current used on a pixel-by-pixel basis, hindering control of the duration of light emission.
There has been an increasing demand for taking photographs and transmitting them to others and for displaying images sent from others. To meet this demand, as shown in FIG. 1, a computer system includes a separate camera 2, in addition to a monitor 1, so that a user may photograph and view objects, and send and receive such images. The computer system In FIG. 1 also includes a main frame 3 and a keyboard 4. Since a conventional display device, such as the monitor 1, can only display an image, the separate camera 2 is required to photograph an object.
In order for the use to be photographed while allowing the user to still view an image on the display device, the camera must be positioned away from the display device. This positioning prevents a photograph of the full face of the user looking at the display device, thus reducing the liveliness of the interactive visual communication.